Remove hints from text views of the test app

They seem to interfere with instrumented the tests execution

Author: wzieba

app/src/main/res/layout/activity_main.xml

@@ -30,7 +30,6 @@
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
                 android:gravity="top|start"
-                android:hint="@string/edit_hint"
                 android:inputType="textCapSentences|textMultiLine"
                 android:paddingEnd="16dp"
                 android:paddingLeft="16dp"
@@ -46,7 +45,6 @@
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
                 android:gravity="top|start"
-                android:hint="@string/source_hint"
                 android:inputType="textNoSuggestions|textMultiLine"
                 android:paddingEnd="16dp"
                 android:paddingLeft="16dp"